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bio website lightandmatter.com
location Fullerton, California
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I teach physics at Fullerton College, a community college in Southern California. I have an undergrad degree in math and physics from Berkeley and a PhD in physics from Yale. Back when I was doing research, my field was experimental low-energy nuclear physics.


Sep
16
comment Wormholes, time travel, and time dilation
the world line of y is curved because it depicts its journey out and back, while x is straight because it has remained stationary? Right. Even though an observer can still see x, it also exists in the past and in synchronized with y? I'm not sure what you mean by this. In relativity, talking about what observers can "see" isn't usually a good idea. Seeing works by propagation of rays of light, which happens at a finite speed.
Sep
16
revised Wormholes, time travel, and time dilation
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Sep
16
revised Wormholes, time travel, and time dilation
added 275 characters in body
Sep
16
comment Wormholes, time travel, and time dilation
@KevinP.Kilburn: The wormholes are created before the diagram begins. B is the point where you enter y. C is the point where you exit x. I'll edit the answer to try to clarify this.
Sep
15
comment Wormholes, time travel, and time dilation
OK. I think this agrees with the claim in Morris 1988. Does the argument in my answer seem to make sense? I'm having to fill in some of the logic that Morris didn't make explicit, so I could be wrong.
Sep
15
comment Deriving Ampère's Circuital Law from Ampère's Force Law?
There are probably many different ways to slice this kind of thing up into a set of axioms and theorems. One possible approach is given in ch. 10 of my SR book, lightandmatter.com/sr . I explicitly list four assumptions in section 10.3.1. This leads through a plausibility argument to the existence of a magnetic field and the Lorentz force law. Section 10.7 then gives a plausibility argument for Maxwell's equations. I don't claim it's a rigorous proof, but I think it shows that if you're trying to construct a reasonable theory, you end up with Maxwell's equations.
Sep
15
comment Deriving Ampère's Circuital Law from Ampère's Force Law?
For something that I think basically amounts to the converse, see physics.stackexchange.com/questions/20477/…
Sep
15
revised Wormholes, time travel, and time dilation
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Sep
15
answered Wormholes, time travel, and time dilation
Sep
15
comment Wormholes, time travel, and time dilation
I've read conflicting info Please point us to your sources. E.g., authors.library.caltech.edu/6469 ?
Sep
14
answered Concept of worldline
Sep
14
comment Recommendation on ADM mass and Bondi mass
How about a link to the ADM paper?
Sep
14
revised Recommendation on ADM mass and Bondi mass
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Sep
14
comment Do eye-glasses decrease the Depth of focus?
It might actually be more natural to measure depth of field in terms of $\Delta(1/x)$ rather than $\Delta x$.
Sep
14
answered Recommendation on ADM mass and Bondi mass
Sep
14
comment Do eye-glasses decrease the Depth of focus?
I think this probably depends on your preferred definition of depth of field. I'm nearsighted, so I could say that without glasses, my depth of field, measured as a length, is about 1 meter. Looking through the tops of my bifocals, I can see stars that are ten light-years away, and I can also comfortably focus as close as about 2 meters. Does this mean that my depth of field improved by some gigantic factor? Well, maybe, but it sort of depends on how you define it.
Sep
13
comment Numerical tests of Titius–Bode formula for artificial planetary orbits
@PiotrMigdal: As far as I can tell, this question is a subset of that one.
Sep
13
awarded  Good Answer
Sep
13
awarded  Nice Answer
Sep
13
comment Numerical tests of Titius–Bode formula for artificial planetary orbits
possible duplicate of Why do the planets' orbital distances fall on an exponential curve?